Measuring the amount of water in a subject's body is essential for diagnosing and for treating medical conditions. Dehydration in a living body is a pathological condition in which water is reduced and often occurs when a person is exercising or when the temperature is high because a lot of water is excreted from the body by sweating to reduce an elevated body temperature. Elderly people are more likely to experience dehydration than general healthy people because of deterioration in the water retention ability in the body.
Generally, when water, in a living body, is reduced by 3% or more of the body weight, body temperature regulation is disturbed. This disturbation of body temperature regulation causes the body temperature to increase, and then water in the living body is further reduced. In other words, a vicious cycle of dehydration is created, which leads to, at last, a pathological condition called heat illness. Heat illness includes conditions such as heat cramp, heat exhaustion, and heatstroke. In some cases, all the organs in the body are affected by heat illness. Thus, it is important to accurately measure the amount of water in the body to avoid the risk of a heat illness.
The armpit is generally a suitable region of the body to obtaining accurately the amount of water in the subject's body. A device to measure the amount of water in a person's body may have a sensor unit with electrodes arranged thereon that measures the capacitance between the electrodes while applying the sensor unit to the armpit to calculate the amount of water in the subject's body.
FIGS. 12 and 12a show diagrams illustrating an example of a device 1200 for measuring the amount of water in a subject's body. As illustrated in FIGS. 12 and 12a, the device 1200 is provided with a main body part 1210 and an insertion part 1220. The main body part 1210 can be grasped, by a measurer (e.g., a nurse or care giver). The main body part 1210 can be formed in a linear shape. A display unit 1212 may be arranged on the surface of a casing of the main body part 1210 to display, for example, a measurement result 1231 thereon. The insertion part 1220 can be inserted into the armpit as the insertion part 1220 extends from one end of the main body part 1210 and can be gently curved relative to the main body part 1210.
A sensor unit 1221 can be slidably supported on a tip surface 1222 of the insertion part 1220. The sensor unit 1221 may include a sensor head 1223, which has a surface substantially parallel to the tip surface 1222. The sensor unit 1221 is biased in a direction indicated by an arrow 1241b, to gain a pressing force for ensuring close contact between the sensor head 1223 and the skin of a subject. When the sensor head 1223 is pressed against the skin of the armpit of a subject, the sensor unit 1221 slides in a direction indicated by an arrow 1241a by a predetermined distance and measurement is started accordingly.